The present invention relates to a draw frame and to a process for the operation of a draw frame in processing a plurality of fiber slivers produced in carders and fed to the draw frame.
Autolevellers such as the RSB 851 of the firm Rieter Ingolstadt with drafting equipment including draw-in and delivery rollers, a main motor and a variable-speed motor are known in the art. The variable-speed motor is superimposed on the main motor with respect to the rotational speed of the draw-in rollers of the draw frame. The main motor, in addition to driving the draw-in rollers, is in particular used to drive the delivery rollers and thereby determines the delivery speed of the drafting equipment. If it is found by means of a measuring system, by means of which the thickness of the entering fiber slivers is measured, that the measured thickness deviates from a pre-set desired value, the draw-in speed of the fiber sliver is accelerated or reduced by means of the variable-speed motor. The delivery speed on the other hand remains always constant. This system ensures constant delivery speed independently of the levelling function. The draw-in speed of the fiber sliver is on the other hand constantly changed. In case of breakage of a presented fiber sliver, the system reacts as it would in case of an extremely think sliver presentation, i.e. the draw-in speed of the remaining slivers is increased. If, in addition, there are also thin spots in the remaining slivers, levelling may sometimes not adhere exactly to the desired value of the drafted fiber sliver. In feeding of fiber slivers without cans from several carders to the draw frame, the requirement of fiber slivers is furthermore so great in case of breakage of a fiber sliver that the carders are unable to present the needed fiber slivers in spite of maximum delivery. Also, intercalated sliver stores are used up within a short time, so that the draw frame must be switched off after the short time. Where slivers are fed by means of cans, the time between the can replacements is also clearly shortened, so that more operator intervention is needed here.
Spinning lines consisting of a carder and a downstream draw frame are known from DE-OS 15 10 481. Between carder and draw frame, a storage is provided which equalizes differences in delivery from the carder to meet the fiber sliver requirement of the draw frame. It is a disadvantage in such a system that when the carder stops, the sliver storage is very quickly exhausted. The draw frame therefore receives no more fiber sliver material for further processing and therefore also stops. Since the draw frame does not contain any levelling device, the adherence to a required fiber sliver thickness is furthermore not possible when a fiber sliver is missing at the intake.
An installation consisting of a draw frame and several upstream carders is known from CH-PS 400 855. The fiber slivers produced in the carders are fed to the draw frame by means of a conveyor belt. Between carder and conveyor belt is a sliver storage in order to equalize differences between carder delivery and draw frame requirement. Thanks to the assignment of several carders to one draw frame, the reserve of fiber sliver available to the draw frame is greater, but still not sufficient for modern, very rapidly working draw frames.
It is therefore also a disadvantage in this system that when the carder is stopped, and following the consumption of the fiber sliver stored in the intercalated fiber storage, the draw frame is also quickly running out of material for further processing and must therefore be stopped. In this case it is also not an autoleveller.